- If an expression contains more than one of the same operator, the evaluation precedence is left to right.
- If an expression contains a combination of logical operators, the order of evaluation is as follows:
- Parentheses can be used to establish the desired evaluation precedence.
- The logical expressions in a conditional expression are not always evaluated left to right.
Avoid using a conditional expression if its accuracy depends on the order in which its logical expressions are evaluated.
For example, compare the following two expressions:
F2/(NULLIF(F1,0)) > 500 F1 <> 0 AND F2/F1 > 500
The first expression guarantees exclusion of division by zero.
The second allows the possibility of error, because the order of its evaluation determines the exclusion of zeros.
The following rules apply to evaluation order for conditional expressions: